The present invention relates to a hydraulic axial bearing for a radially-supported rotatable shaft or axle.
There is a need within many fields of technology for an axially-adjustable bearing system, which can withstand heavy and variable axial thrust loads. One example of this is in the cellulose processing industry, where a multi-purpose axial mill can be subjected to thrust loads on the order of 100 tons, while at the same time having to satisfy high demands for accuracy in axial positioning, in order to achieve an exact grinding gap.
A similar axial bearing system is known from the PCT publication WO 88/03611, which contains a detailed description of the general requirements for a hydrostatic bearing system and hydrostatic axial-bearing systems of the prior art.
The axial bearing system mentioned in the PCT publication uses two hydrostatic axial bearings, one on either side of a flange-like pressure plate which is anchored to the shaft or is formed integrally with it. Another system is shown in SE 464 370, where two flanges are used instead of one, with the bearings acting in opposed directions, away from one another.
Both these designs have practical limitations, mainly in respect of the difficulty of maintaining the inner and outer sealing gaps at the same height in spite of deflections caused by loads and thermal expansion. A deviation as small as 1/100 mm can have disastrous consequences. In addition, the bearing is relatively heavy, with a high moment of inertia, which is a great disadvantage in absorbing vibrations of the flange. The bearing is also very expensive due to its weight.